Being able to call lightning requires the power to manipulate clouds to make lightning, which happens to also let you manipulate the weather somewhat. She’s been slowly drawing in the clouds and the typhoon so it arrived earlier than expected and thus goes away before the festival.
I got a bit confused there with the explanation of how calling lightning affects the storm.
The teacher explained it in this panel:
Being able to call lightning requires the power to manipulate clouds to make lightning, which happens to also let you manipulate the weather somewhat. She’s been slowly drawing in the clouds and the typhoon so it arrived earlier than expected and thus goes away before the festival.
Oh… That does make sense.